Deep Learning Enhanced Electrochemiluminescence Microscopy

Electrochemiluminescence Microscopy

Electrochemiluminescence (ECL) is rapidly evolving from an analytical method into an optical microscopy. The orthogonality of the electrochemical trigger and the optical readout distinguishes it from classic microscopy and electrochemical techniques, owing to its near-zero background, remarkable sensitivity, and absence of photobleaching and phototoxicity. In this minireview, we summarize the recent advances in ECL imaging technology, emphasizing original configurations which enable the imaging of biological entities and the improvement of the analytical properties by increasing the complexity and multiplexing of bioassays. Additionally, mapping the (electro)chemical reactivity in space provides valuable information on nanomaterials and facilitates deciphering ECL mechanisms for improving their performances in diagnostics and (electro)catalysis. Finally, we highlight the recent achievements in imaging at the ultimate limits of single molecules, single photons or single chemical reactions, and the current challenges to translate the ECL imaging advances to other fields such as material science, catalysis and biology.

AI-Assisted Real-Time Immunoassay Improves Clinical Sensitivity and Specificity

Real-time biosensing systems can interrogate the association between the analyte and the biorecognition element across time. Typically, the resulting data are preprocessed to offer valuable bioanalytical information obtained at a single optimal point of such a real-time response; for instance, a diagnosis of certain medical conditions can be established depending on a biomarker (analyte) concentration measured at an optimal time, that is, a threshold. Exploiting this conventional approach, we previously developed a nanophotonic immunoassay for bacterial vaginosis diagnosis exhibiting a clinical sensitivity and specificity of ca. 96.29% (n = 162). Herein, we demonstrate that a real-time biosensing platform assisted by artificial intelligence not only obviates biomarker concentration (i.e., a threshold) determination but also increases sensitivity and specificity in the targeted diagnostic, thereby reaching values of up to 100%.

An enhanced multimode phase imaging method based on the transport of intensity equation

Label-free biological cell imaging relies on rapid multimode phase imaging of biological samples in natural settings. To improve image contrast, phase is encoded into intensity information using the differential interference contrast (DIC) and Zernike phase contrast (ZPC) techniques. To enable multimode contrast-enhanced observation of unstained specimens, this paper proposes an improved multimode phase imaging method based on the transport of intensity equation (TIE), which combines conventional microscopy with computational imaging. The ZPC imaging module based on adaptive aperture adjustment is applied when the quantitative phase results of biological samples have been obtained by solving the TIE. Simultaneously, a rotationally symmetric shear-based technique is used that can yield isotropic DIC. In this paper, we describe numerical simulation and optical experiments carried out to validate the accuracy and viability of this technology. The calculated Michelson contrast of the ZPC image in the resolution plate experiment increased from 0.196 to 0.394.

Sub-Second Electrochemiluminescence Imaging Assay of SARS-CoV-2 Nucleocapsid Protein Based on Reticulation of Endo-Coreactants

The nonphotodriven electrochemiluminescence (ECL) imageology necessitates concentrated coreacting additives plus longtime exposures. Seeking biosafe and streamlined ensembles can help lower the bar for quality ECL bioimaging to which call the crystallized endo-coreaction in nanoreticula might provide a potent solution. Herein, an exo-coreactant-free ECL visualizer was fabricated out in one-pot, which densified the dyad triethylamine analogue: 1,4-diazabicyclo-[2.2.2]octane (DABCO) in the lamellar hive of 9,10-di(p-carboxyphenyl)anthracene (DPA)-Zn2+. This biligated non-noble metal-organic framework (m-MOF) facilitated a self-contained anodic ECL with a yield as much as 70% of Ru(bPy)32+ in blank phosphate buffered saline. Its featured two-stage emissions rendered an efficient and endurant CCD imaging at 1.0 V under mere 0.5 s swift snapshots and 0.1 s step-pulsed stimulation. Upon structural and spectral cause analyses as well as parametric set optimization, simplistic ECL-graphic immunoassay was mounted in the in situ imager to enact an ultrasensitive measurement of coronaviral N-protein in both signal-on and off modes by the privilege of straight surface amidation on m-MOFs, resulting in a wide dynamic range (10-4-10 ng/mL), a competent detection limit down to 56 fg/mL, along with nice precision and parallelism in human saliva tests. The overall work manifests a rudimentary endeavor in self-sufficient ECL visuality for brisk, biocompatible, and brilliant production of point-of-care diagnostic "Big Data".

Optics Determines the Electrochemiluminescence Signal of Bead-Based Immunoassays

Electrochemiluminescence (ECL) is an optical readout technique that is successfully applied for the detection of biomarkers in body fluids using microbead-based immunoassays. This technology is of utmost importance for in vitro diagnostics and thus a very active research area but is mainly focused on the quest for new dyes and coreactants, whereas the investigation of the ECL optics is extremely scarce. Herein, we report the 3D imaging of the ECL signals recorded at single microbeads decorated with the ECL labels in the sandwich immunoassay format. We show that the optical effects due to the light propagation through the bead determine mainly the spatial distribution of the recorded ECL signals. Indeed, the optical simulations based on the discrete dipole approximation compute rigorously the electromagnetic scattering of the ECL emission by the microbead and allow for reconstructing the spatial map of ECL emission. Thus, it provides a global description of the ECL chemical reactivity and the associated optics. The outcomes of this 3D imaging approach complemented by the optical modeling provide insight into the ECL optics and the unique ECL chemical mechanism operating on bead-based immunoassays. Therefore, it opens new directions for mechanistic investigations, ultrasensitive ECL bioassays, and imaging.